Because of restricted or limited areas of operation, it
is not always possible to take off or land the seaplane directly into the
wind. Such restricted areas may be canals or narrow rivers. Therefore,
skill must be acquired in crosswind techniques to enhance the safety of
seaplane operation.

The forces developed by crosswinds during takeoffs or landings
on water are almost the same as those developed during similar operations
on land. Directional control is more difficult because of the more yielding
properties of water, less surface friction, and lack of nosewheel, tailwheel,
or brakes. Though water surface is more yielding than solid land, a seaplane
has no shock absorbing capability, so all the shock is absorbed by the
hull or floats and transmitted to the aircraft structure.

As shown in Fig. 15-11, a crosswind tends to push the seaplane
sideways. The drifting force, acting through the seaplane's center of gravity,
is opposed by the water reacting on the area of the floats or hull in contact
with the water. This results in a tendency to weathervane into the wind.
Once this weathervaning has started, the turn continues and is further
aggravated by the addition of centrifugal force acting outward from the
turn, which again is opposed by the water reaction on the floats or hull.
If strong enough, the combination of the wind and centrifugal force may
tip the seaplane to the point where the downwind float will submerge and
subsequently the wingtip may strike the water and capsize the seaplane.
This is known as a "waterloop" similar to a "groundloop" on land.

Because of the lack of clear reference lines for directional
guidance, such as are found on airport runways, it is difficult to quickly
detect sidedrift on water. Fortunately, early detection of sidedrift is
not really essential, because the seaplane takeoff and landing can be made
without maintaining a straight line while in contact with the water. A
turn should be made toward the downwind side after landing. This will allow
the seaplane to dissipate its forward speed prior to its weathervaning
into the wind. By doing this, centrifugal force while weathervaning will
be kept to a minimum and better aircraft control will result with less
turnover tendency.

One technique sometimes used to compensate for crosswinds
during water operations is the same as that used on land; that is, by lowering
the upwind wing while holding a straight course with rudder. This creates
a slip into the wind to offset the drifting tendency. The upwind wing is
held in the lowered position throughout the touchdown and until completion
of the landing.

Another technique used to compensate for crosswinds (preferred
by many seaplane pilots) is the downwind arc method. Using this method,
the pilot creates a sideward force (centrifugal force) that will offset
the crosswind force. This is accomplished by steering the seaplane in a
downwind arc as shown in Fig. 15-11. The pilot merely plans an arced path
and follows this arc to produce sufficient centrifugal force so that the
seaplane will tend to lean outward against the wind force. During the run,
the pilot can adjust the rate of turn by varying rudder pressure, thereby
increasing or decreasing the centrifugal force to compensate for a changing
wind force.

In practice, it is quite simple to plan sufficient curvature
of the takeoff path to cancel out strong crosswinds, even on very narrow
rivers. As illustrated in Fig. 15-12, the takeoff is started at the lee
side of the river with the seaplane heading slightly into the wind. The
takeoff path is then gradually made in an arc away from the wind and the
liftoff accomplished on the downwind edge of the river. This pattern also
allows for more climbout space into the wind.

It should be noted that the greatest degree of the downwind
arc is during the time the seaplane is traveling at the slower speeds of
takeoff or landing. At the faster speeds, the crosswind effect lessens
considerably, and at very slow speeds the seaplane can weathervane into
the wind with no ill effect.

Unless the current is extremely swift, crosswind or calm
wind takeoffs and landings in rivers or tidal flows should be made in the
same direction as the current. This reduces the water forces on the floats
or hull of the seaplane.

Again, experience will play an important part in successful
seaplane operation during crosswinds. It is essential that all seaplane
pilots have thorough knowledge and skill in these maneuvers.